6.3 Backannotation

Backannotation is the process of setting VITAL generics with timing
information provided by an external files.

The external files must be SDF (Standard Delay Format) files. GHDL
supports a tiny subset of SDF version 2.1, other version number can be
used, provided no features added by the next version are used.

Hierarchical instance names are not supported. However you can use a list of
instances. If there is no instance, the top entity will be annotated and
the celltype must be the name of the top entity. If there is at least one
instance, the last instance name must be a component instantiation label, and
the celltype must be the name of the component declaration instantiated.

Instances being annotated are not required to be VITAL compliant. However
generics being annotated must follow rules of VITAL (e.g., type must be a
suitable vital delay type).

Currently, only timing constraints applying on a timing generic of type
VitalDelayType01 has been implemented. This SDF annotator is
just a proof of concept. Features will be added with the following GHDL
release.